Event: Avoid illegal multiplication for memset

Because "file_events" is "FileEvent" type and adding an integral value to
this pointer automatically scales that value by the size.

Signed-off-by: Haomai Wang <haomaiwang@gmail.com>
Merge pull request #3265 from yuyuyu101/coverify-fix

Event: Avoid illegal multiplication for memset

Reviewed-by: Sage Weil <sage@redhat.com>